A large number of fire engines now incorporate electronic controls and more specifically, electronic controls for determining the speed of the engine during pumping service where that control is handled externally from the pump control panel. Presently a Morse or Felsted control is used whereby rotary motion is mechanically converted to linear motion, that control being mounted on the control panel. The term "Morse control" will be used hereinafter to refer to both such controls and any other equivalent. The portion of the Morse control extending inwardly from the panel couples to a throttle cable, which cable then connects at some previously thought-to-be convenient point to a potentiometer, the output of which is connected to the electronic control for controlling the speed of the engine. The electronic control normally is mounted in the cab of the fire truck and the pump control panel is mounted on the body some distance rearwardly from the electronic control. The throttle cable coupled to the Morse control is normally housed within a sheath made of plastic or similar material and extends approximately ten feet within the sheath from the interior end of the Morse control to the vicinity of the potentiometer. Because of the need to attach the cable to the potentiometer cable, a splice is necessary. The potentiometer has been located at some point remote from the pump control panel, between that and the electronic control in the fire truck cab.
The Morse control itself is a readily available component which may be termed a mechanical vernier throttle control unit. Rotating the external control knob counterclockwise causes linear motion of an inwardly projecting rod having a connector such as a ball on the innermost end of the rod to move outward. When the proper engine speed is achieved, the Morse control stays positively fixed at that position. It may be released by rotating the control knob in the opposite direction and it has the feature of a pop-release, whereby hitting the release button at the center of the external control knob causes the central rod to move rapidly to its home position which is minimum throttle position for the engine.
One of the problems relating to the prior structure of connecting a cable from the Morse control to a potentiometer at some location between the Morse control and the electronic control on the engine is that it requires mechanical attachments and a run of cable. These are mechanical means which are subject to failure. It is also difficult to achieve any precision of control with such a device. However, this structure has been used and has been relatively satisfactory and was devised and accepted by engineers of major fire engine manufacturers, since no other means has been available up to the present time.